Magnetic tunnel junction structure of magnetic random access memory cell

ABSTRACT

A magnetic tunnel junction (MTJ) structure of a magnetic random access memory (MRAM) cell includes an insulation layer, a patterned MTJ film stack, an aluminum oxide protection layer, an interlayer dielectric, and a connection structure. The patterned MTJ film stack is disposed on the insulation layer. The aluminum oxide protection layer is disposed on a sidewall of the patterned MTJ film stack, and the aluminum oxide protection layer includes an aluminum film oxidized by an oxidation treatment. The interlayer dielectric covers the aluminum oxide protection layer and the patterned MTJ film stack. The connection structure penetrates the interlayer dielectric above the patterned MTJ film stack, and the connection structure is electrically connected to a topmost portion of the patterned MTJ film stack.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 15/803,852filed on Nov. 6, 2017, now allowed, which is incorporated by referenceherein in its entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a magnetic tunnel junction (MTJ)structure of a magnetic random access memory (MRAM) cell, and moreparticularly, to a MTJ structure of a MRAM cell including an aluminumoxide protection layer.

2. Description of the Prior Art

There are essentially two types of data memory devices used inelectronic products, non-volatile and volatile memory devices. Magneticrandom access memory (MRAM) is a kind of non-volatile memory technology.Unlike current industry-standard memory devices, MRAM uses magnetisminstead of electrical charges to store data. In general, MRAM cellsinclude a data layer and a reference layer. The data layer is composedof a magnetic material and the magnetization of the data layer can beswitched between two opposing states by an applied magnetic field forstoring binary information. The reference layer can be composed of amagnetic material in which the magnetization is pinned so that thestrength of the magnetic field applied to the data layer and partiallypenetrating the reference layer is insufficient for switching themagnetization in the reference layer. During the read operation, theresistance of the MRAM cell is different when the magnetizationalignments of the data layer and the reference layer are the same ornot, and the magnetization polarity of the data layer can be identifiedaccordingly.

Generally, the manufacturing process of the MRAM cell can be integratedwith the conventional semiconductor manufacturing processes ofintegrated circuits. However, the magnetic properties of ferromagneticlayers may be deteriorated by related manufacturing processes and theperformance of the MRAM cell may be influenced accordingly.

SUMMARY OF THE INVENTION

A magnetic tunnel junction (MTJ) structure of a magnetic random accessmemory (MRAM) cell is provided by the present invention. In the MTJstructure, an aluminum film is formed on a sidewall of a patterned MTJfilm stack, and the aluminum film is oxidized by an oxidation treatmentfor forming an aluminum oxide protection layer on the sidewall of thepatterned MTJ film stack. The aluminum oxide protection layer may beused to isolate different layers in the patterned MTJ film stack withoutinfluencing the magnetic properties of the patterned MTJ film stack.

According to one embodiment of the present invention, a MTJ structure ofa MRAM cell is provided. The MTJ structure of the MRAM cell includes aninsulation layer, a patterned MTJ film stack, an aluminum oxideprotection layer, an interlayer dielectric, and a connection structure.The patterned MTJ film stack is disposed on the insulation layer. Thealuminum oxide protection layer is disposed on a sidewall of thepatterned MTJ film stack, and the aluminum oxide protection layerincludes an aluminum film oxidized by an oxidation treatment. Theinterlayer dielectric covers the aluminum oxide protection layer and thepatterned MTJ film stack. The connection structure penetrates theinterlayer dielectric above the patterned MTJ film stack, and theconnection structure is electrically connected to a topmost portion ofthe patterned MTJ film stack.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-5 are schematic drawings illustrating a manufacturing method ofa magnetic random access memory (MRAM) cell according to a firstembodiment of the present invention, wherein FIG. 2 is a schematicdrawing in a step subsequent to FIG. 1, FIG. 3 is a schematic drawing ina step subsequent to FIG. 2, FIG. 4 is a schematic drawing in a stepsubsequent to FIG. 3, and FIG. 5 is a schematic drawing in a stepsubsequent to FIG. 4.

FIG. 6 is a schematic drawing illustrating a manufacturing method of aMRAM cell according to a second embodiment of the present invention.

FIGS. 7-9 are schematic drawings illustrating a manufacturing method ofa MRAM cell according to a third embodiment of the present invention,wherein FIG. 8 is a schematic drawing in a step subsequent to FIG. 7,and FIG. 9 is a schematic drawing in a step subsequent to FIG. 8.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth,such as particular structures, components, materials, dimensions,processing steps and techniques, in order to provide a thoroughunderstanding of the present invention. However, it will be appreciatedby one of ordinary skill in the art that the invention may be practicedwithout these specific details. In other instances, well-knownstructures or processing steps have been described in detail in order toavoid obscuring the invention.

It will be understood that when an element is referred to as being“formed” on another element, it can be directly or indirectly, formed onthe given element by growth, deposition, etch, attach, connect, orcouple. And it will be understood that when an elements or a layer isreferred to as being “on”, “connected to”, or “coupled to” anotherelement or layer, it can be directly on, connected or coupled to theother element or layer or intervening elements or layers may be present.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. These terms are only usedto distinguish one element, component, region, layer and/or section fromanother. Thus, a first element, component, region, layer or sectiondiscussed below could be termed a second element, component, region,layer or section without departing from the teachings of the disclosure.

Please refer to FIGS. 1-5. FIGS. 1-5 are schematic drawings illustratinga manufacturing method of a magnetic random access memory (MRAM) cellaccording to a first embodiment of the present invention. Themanufacturing method of the MRAM cell in this embodiment includes thefollowing steps. As shown in FIG. 1, a magnetic tunnel junction (MTJ)film stack 30 is formed on an insulation layer 10. In some embodiments,the MTJ film stack 30 may include a first conductive layer 31, a pinnedlayer 32, a first barrier layer 33, a free layer 34, a second barrierlayer 35, and a second conductive layer 36 sequentially formed on theinsulation layer 10 in a thickness direction (such as a perpendiculardirection Z shown in FIG. 1), but not limited thereto. The components ofthe MTJ film stack 30 may be modified and/or include other materiallayers according to other design considerations. In some embodiments,the first conductive layer 31 and the second conductive layer 36 mayinclude metallic materials, such as tantalum (Ta), platinum (Pt),ruthenium (Ru), a stack layer of the above-mentioned materials, an alloyof the above-mentioned materials, or other suitable conductivematerials. The pinned layer 32 may include a synthetic antiferromagneticlayer and a reference layer. The synthetic antiferromagnetic layer mayinclude antiferromagnetic materials such as iron manganese (FeMn) orcobalt/platinum (Co/Pt) multilayer for a perpendicularly magnetized MTJ,but not limited thereto. The free layer 34 and the reference layer inthe pinned layer 32 may include ferromagnetic materials such as cobalt,iron (Fe), cobalt-iron (CoFe), cobalt-iron-boron (CoFeB), or othersuitable ferromagnetic materials. In addition, the first barrier layer33 and the second barrier layer 35 may include insulation materials suchas magnesium oxide (MgO), aluminum oxide, or other suitable insulationmaterials. The above-mentioned material layers in the MTJ film stack 30may be formed by deposition processes, such as sputtering processes, butnot limited thereto.

In some embodiments, the insulation layer 10 may include silicon oxide,silicon oxynitride, silicon nitride, or other suitable insulationmaterials, and the insulation layer 10 may be formed on a substrate (notshown), such as a silicon substrate, a silicon germanium substrate, or asilicon-on-insulator (SOI) substrate, but not limited thereto.Additionally, a first connection structure 20 may be formed in theinsulation layer 10 before the step of forming the MTJ film stack 30,and the first connection structure 20 may be electrically connected withthe first conductive layer 31 of the MTJ film stack 30, but not limitedthereto. In some embodiments, the first connection structure 20 may beformed by filling a recess in the insulation layer 10 with a barrierlayer (not shown) and a conductive material (not shown), but not limitedthereto. The barrier layer in the first connection structure 20 mayinclude titanium nitride, tantalum nitride, or other suitable barriermaterials, and the conductive material in the first connection structure20 may include materials with relatively lower resistivity, such ascopper, aluminum, or tungsten, but not limited thereto. In someembodiments, the first connection structure 20 may be connecteddownwards to other units or circuits (not shown) in the substratementioned above, but not limited thereto. In other words, the firstconnection structure 20 may be formed by the process of forming aninterconnection structure on the substrate.

As shown in FIG. 1, an aluminum mask layer 40 may be formed on the MTJfilm stack 30, and a hard mask layer 50 may be formed on the aluminummask layer 40. In some embodiments, the hard mask layer 50 may includeinsulation materials such as silicon nitride, silicon oxynitride, orother suitable insulation materials. The hard mask layer 50 and thealuminum mask layer 40 may be formed by the same patterning process orthe aluminum mask layer may be formed by a patterning process with thehard mask layer as a mask. Therefore, a projection area of the aluminummask layer 40 in the perpendicular direction Z may be similar to aprojection area of the hard mask layer 50 in the perpendicular directionZ, but not limited thereto.

As shown in FIG. 1 and FIG. 2, an ion beam etching (IBE) process 90 isperformed with the aluminum mask layer 40 and the hard mask layer 50 asa mask for etching a part of the MTJ film stack 30 which is not coveredby the aluminum mask layer 40 and the hard mask layer 50. The MTJ filmstack 30 is patterned to be a patterned MTJ film stack 30P by the IBEprocess 90. The first conductive layer 31 in the MTJ film stack 30 maybe patterned to be a bottom electrode 31E by the IBE process 90, and thesecond conductive layer 36 in the MTJ film stack 30 may be patterned tobe a top electrode 36E by the IBE process 90. Accordingly, the patternedMTJ film stack 30P may include the bottom electrode 31E, the pinnedlayer 32, the first barrier layer 33, the free layer 34, the secondbarrier layer 35, and the top electrode 36E. The pinned layer 32 isformed on the bottom electrode 31E. The first barrier layer 33 is formedon the pinned layer 32. The free layer 34 is formed on the first barrierlayer 33. The second barrier layer 35 is formed on the free layer 33.The top electrode 36E is formed on the second barrier layer 35. Thefirst connection structure 20 in the insulation layer 10 may beelectrically connected with the bottom electrode 31E of the patternedMTJ film stack 30P, and the first connection structure 20 may be formedin the insulation layer 10 before the IBE process 90, but not limitedthereto. In some embodiments, a part of the insulation layer 10 may beremoved by the IBE process 90, but not limited thereto. Therefore, theinsulation layer 10 under the patterned MTJ film stack 30P in theperpendicular direction Z may have a sidewall (such as a second sidewallSW2 shown in FIG. 2) substantially aligned with a sidewall (such as afirst sidewall SW1 shown in FIG. 2) of the patterned MTJ film stack 30P,but not limited thereto. In some embodiments, an argon (Ar) bombardment91 may be used in the IBE process 90 for patterning the MTJ film stack30. Specifically, the process gas applied in the IBE process 90 mayinclude Ar, oxygen, xenon (Xe), or other suitable gas for etchingdifferent kinds of material layers of the MTJ film stack 30, and atleast some of the process gas may be used as a bombardment source of theIBE process 90, but not limited thereto.

As shown in FIG. 2 and FIG. 3, at least a part of the aluminum masklayer 40 is bombarded by the IBE process 90 for forming an aluminum film41 on a sidewall (such as the first sidewall shown in FIG. 3) of thepatterned MTJ film stack 30P. In some embodiments, the aluminum film 41may be a part of the aluminum mask layer 40 bombarded by the Arbombardment 91 of the IBE process 90 and reflow on the sidewall of thepatterned MTJ film stack 30P, and at least a part of the hard mask layer50 may be removed by the Ar bombardment 91 of the IBE process 90, butnot limited thereto. In some embodiments, the aluminum film 41 may alsobe formed by other kinds of bombardments used in the IBE process 90. Inthe IBE process 90, the hard mask layer 50 may be used to control thetiming of forming the aluminum film 41, and the aluminum film 41 has tobe formed after the step of forming the patterned MTJ film stack 30P.Therefore, the thickness of the hard mask layer 50 has to be controlledfor covering the aluminum mask layer 40 during the step of forming thepatterned MTJ film stack 30P, and at least a part of the aluminum masklayer 40 has to be exposed to the Ar bombardment 91 after the step offorming the patterned MTJ film stack 30P. In some embodiments, a part ofthe insulation layer 10 may be removed by the Ar bombardment 91 afterthe step of forming the patterned MTJ film stack 30P and before the stepof forming the aluminum film 41, and the aluminum film 41 may be furtherformed on a sidewall (such as the second sidewall SW2 shown in FIG. 3)of the insulator layer 10 under the patterned MTJ film stack 30P.Therefore, the patterned MTJ film stack 30P may be encompassed by thealuminum film 41 and the aluminum mask layer 40 after the Ar bombardment91.

As shown in FIG. 3 and FIG. 4, an oxidation treatment 92 may beperformed after the Ar bombardment 91, and the aluminum film 41 may beoxidized to be an aluminum oxide protection layer 41X on the sidewall(such as the first sidewall shown in FIG. 4) of the patterned MTJ filmstack 30P by the oxidation treatment 92. In some embodiments, theoxidation treatment 92 may be a part of the IBE process 90, and theoxidation treatment 92 may be regarded as an in-situ oxidation treatmentperformed in the same process chamber where the step of patterning theMTJ film stack 30 is performed, but not limited thereto. In someembodiments, the oxidation treatment 92 may be performed after the IBEprocess 90 and the oxidation treatment 92 may be performed in a processchamber different from that of the IBE process 90. During the oxidationtreatment 92, oxygen ion beams may be used to oxidize metal into metaloxide especially when the oxidation treatment 92 is a part of the IBEprocess 90, but not limited thereto. In some embodiments, other kinds ofoxidation approaches may also be applied in the oxidation treatment 92.It is worth noting that, in some embodiments, other metal residues(except aluminum) of the IBE process 90 may also be oxidized by theoxidation treatment 92 to be insulation metal oxide on the sidewall ofthe patterned MTJ film stack 30P, but not limited thereto. In someembodiments, at least a part of the aluminum mask layer 40 may beoxidized by the oxidation treatment 92, and an aluminum oxide layer 40Xmay be formed on the surface of the aluminum mask layer 40 by theoxidation treatment 92. The aluminum oxide layer 40X may be connectedwith the aluminum oxide protection layer 41X formed on the sidewall ofthe patterned MTJ film stack 30P, and the patterned MTJ film stack 30Pmay be encompassed by the aluminum oxide protection layer 41X, thealuminum oxide layer 40X, and the aluminum mask layer 40, but notlimited thereto.

As shown in FIG. 5, an interlayer dielectric 60 may be formed and coverthe aluminum oxide protection layer 41X, the aluminum oxide layer 40X,the aluminum mask layer 40, the insulation layer 10, and the patternedMTJ film stack 30P. The interlayer dielectric 60 may be a single layeror multilayer structure. For example, the interlayer dielectric 60 mayinclude a first dielectric layer 61 and a second dielectric layer 62formed on the first dielectric layer 61. The first dielectric layer 61and the second dielectric layer 62 may include dielectric materials suchas silicon nitride, silicon oxide, or other suitable dielectricmaterials. A second connection structure 70 may be formed and penetratethe interlayer dielectric 60 above the patterned MTJ film stack 30P, andthe second connection structure 70 may be electrically connected to atopmost portion of the patterned MTJ film stack 30P. In someembodiments, the second connection structure 70 may penetrate the seconddielectric layer 62 and the aluminum oxide layer 40X and contact thealuminum mask layer 40 directly, and the second connection structure 70may be electrically connected to the topmost portion of the patternedMTJ film stack 30P via the aluminum mask layer 40, but not limitedthereto. In other words, the second connection structure 70 may beelectrically connected to the top electrode 36E of the patterned MTJfilm stack 30P via the aluminum mask layer 40, but not limited thereto.In some embodiments, the second connection structure 70 may furtherpenetrate the aluminum mask layer 40 for directly contacting the topelectrode 36E of the patterned MTJ film stack 30P. The materials and themanufacturing method of the second connection structure 70 may besimilar to those of the first connection structure 20 mentioned above,but not limited thereto. A MRAM cell 101 as shown in FIG. 5 may beformed by the manufacturing steps described above. The aluminum oxide isa non-magnetic insulation material which is great to isolate differentlayers in the patterned MTJ film stack 30P without influencing themagnetic properties of the patterned MTJ film stack 30P. Therefore, thealuminum oxide protection layer 41X and the aluminum oxide layer 40X mayprovide a great protection effect to the patterned MTJ film stack 30Pwithout influencing the magnetic properties of the patterned MTJ filmstack 30P, and the operation performance and manufacturing yield of theMRAM cell 101 may be enhanced accordingly.

The following description will detail the different embodiments of thepresent invention. To simplify the description, identical components ineach of the following embodiments are marked with identical symbols. Formaking it easier to understand the differences between the embodiments,the following description will detail the dissimilarities amongdifferent embodiments and the identical features will not be redundantlydescribed.

Please refer to FIG. 6. FIG. 6 is a schematic drawing illustrating amanufacturing method of a MRAM cell 102 according to a second embodimentof the present invention. As shown in FIG. 6, the difference between themanufacturing method of this embodiment and the manufacturing method ofthe first embodiment is that the aluminum mask layer 40 as shown in FIG.5 of the first embodiment may be removed before the step of forming thesecond connection structure 70 in this embodiment. In other words, theMRAM cell 102 does not include the aluminum mask layer 40 mentionedabove, and the second connection structure 70 may penetrate theinterlayer dielectric 60 above the second connection structure 70 fordirectly contacting the top electrode 36E. In some embodiments, thealuminum mask layer may be removed before the step of forming the seconddielectric layer 62 and after the step of forming the first dielectriclayer 61, but not limited thereto.

Please refer to FIGS. 7-9. FIGS. 7-9 are schematic drawings illustratinga manufacturing method of a MRAM cell 103 according to a thirdembodiment of the present invention. As shown in FIG. 7, a part of thehard mask layer 50 may remain on the aluminum mask layer 40 after the Arbombardment 91, and a part of the aluminum mask layer 40 is not coveredby the aluminum mask layer 40 for being bombarded by the Ar bombardment91 and forming the Ar bombardment 91 on the first sidewall SW1 of thepatterned MTJ film stack 30P and the second sidewall SW2 of theinsulation layer 10 under the patterned MTJ film stack 30P. As shown inFIG. 8, a part of the hard mask layer 50 may still remain on thealuminum mask layer 40 during the oxidation treatment 92, and thealuminum oxide layer 40X may be formed on a part of the surface of thealuminum mask layer 40. As shown in FIG. 8 and FIG. 9, the hard masklayer 50 may be removed before the step of forming the second dielectriclayer 62, and the second connection structure 70 may penetrate theinterlayer dielectric 60 above the second connection structure 70 anddirectly contact the aluminum mask layer 40.

To summarize the above descriptions, in the manufacturing method of theMRAM cell according to the present invention, the aluminum oxideprotection layer is formed on the sidewall of the patterned MTJ filmstack by oxidizing the aluminum film formed by bombarding the aluminummask layer in the IBE process. The aluminum oxide protection layer mayprovide the protection effect to the patterned MTJ film stack withoutinfluencing the magnetic properties of the patterned MTJ film stack. Theoperation performance and manufacturing yield of the MRAM cell may beenhanced accordingly.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A magnetic tunnel junction (MTJ) structure of amagnetic random access memory (MRAM) cell, comprising: an insulationlayer; a patterned MTJ film stack disposed on the insulation layer; analuminum oxide protection layer disposed on a sidewall of the patternedMTJ film stack, wherein the aluminum oxide protection layer comprises analuminum film oxidized by an oxidation treatment; an interlayerdielectric covering the aluminum oxide protection layer and thepatterned MTJ film stack; a connection structure penetrating theinterlayer dielectric above the patterned MTJ film stack, wherein theconnection structure is electrically connected to a topmost portion ofthe patterned MTJ film stack; an aluminum mask layer disposed on thepatterned MTJ film stack, wherein the connection structure iselectrically connected to the topmost portion of the patterned MTJ filmstack via the aluminum mask layer; and an aluminum oxide layer disposedon a sidewall of the aluminum mask layer, wherein the aluminum oxidelayer comprises a part of the aluminum mask layer oxidized by theoxidation treatment.
 2. The MTJ structure of the MRAM cell according toclaim 1, wherein the patterned MTJ film stack is encompassed by thealuminum oxide protection layer and the aluminum mask layer.
 3. The MTJstructure of the MRAM cell according to claim 1, wherein the interlayerdielectric comprises: a first dielectric layer; and a second dielectriclayer disposed on the first dielectric layer, wherein a top surface ofthe first dielectric layer and a top surface of the aluminum mask layerare coplanar, and the connection structure penetrates the seconddielectric layer.
 4. The MTJ structure of the MRAM cell according toclaim 1, wherein the aluminum oxide layer is connected with the aluminumoxide protection layer.
 5. The MTJ structure of the MRAM cell accordingto claim 1, wherein the aluminum oxide layer disposed on the sidewall ofthe aluminum mask layer is disposed between the aluminum mask layer andthe interlayer dielectric, and the interlayer dielectric directlycontacts a top surface of the aluminum mask layer.
 6. The MTJ structureof the MRAM cell according to claim 1, wherein the aluminum oxide layeris further disposed on a top surface of the aluminum mask layer, and theconnection structure further penetrates the aluminum oxide layer on thetop surface of the aluminum mask layer.
 7. The MTJ structure of the MRAMcell according to claim 6, wherein the interlayer dielectric comprises:a first dielectric layer; and a second dielectric layer disposed on thefirst dielectric layer, wherein a top surface of the first dielectriclayer and a top surface of the aluminum oxide layer are coplanar, andthe connection structure penetrates the second dielectric layer.
 8. TheMTJ structure of the MRAM cell according to claim 1, wherein thealuminum oxide protection layer is further disposed on a sidewall of theinsulator layer under the patterned MTJ film stack.
 9. The MTJ structureof the MRAM cell according to claim 8, wherein the sidewall of theinsulator layer is aligned with the sidewall of the patterned MTJ filmstack in a thickness direction of the insulation layer.
 10. The MTJstructure of the MRAM cell according to claim 1, wherein the patternedMTJ film stack comprises: a bottom electrode; a pinned layer disposed onthe bottom electrode; a first barrier layer disposed on the pinnedlayer; a free layer disposed on the first barrier layer; a secondbarrier layer disposed on the free layer; and a top electrode disposedon the second barrier layer.